Oxidation States and Lanthanoid Contraction — Prelims Questions

Which of the following statements about the oxidation states of lanthanoids is INCORRECT?

The gradual decrease in atomic and ionic radii across the lanthanoid series is known as:

Which of the following is a direct consequence of lanthanoid contraction?

What is the electronic configuration of Gd$^{3+}$ (Gadolinium ion)? (Atomic number of Gd = 64)

Which of the following lanthanoid ions is expected to be a strong oxidizing agent?

The basicity of lanthanoid hydroxides, Ln(OH)$_3$, generally decreases from La(OH)$_3$ to Lu(OH)$_3$. This trend is best explained by: